This application relates to masks for protecting persons against the dangers of heat, smoke and toxic gases during a fire emergency and more particularly to such a hood adapted to be used, amongst other uses, in conjunction with emerhency oxygen or air supply systems on aircraft and similar vehicles.
It has long been recognized that in fire emergencies incapacitating toxic gases cause many fatalities which could be avoided if the person could avoid inhaling them. This problem is probably most frequently encountered during low impact aircraft crashes, or beely-landings, when the aircraft does not disintegrate upon impact and encounters damage without completely disintegrating. During such crashes, many or all of the passengers on board survive the initial impact but they are killed by the ensuing fire. The National Transportation Safety Board recently summarized, as follows, the sequence of events surrounding a commercial airline crash in which the sircraft belly-lands.
Initially the aircraft skids along the ground. This shreds fuel lines in the lower fuselage of the aircraft and sprays a fine mist of jet fuel into the baggage compartment. Typically, one of the wings brushes the ground, a wing tank ruptures and more fuel mist sprays out. A spark generated by the aircraft's crushing, skidding underside ignites the vapor and a fireball envelopes the lower fuselage and the wing touching the ground.
Within 30 to 60 seconds of the initial impact, the aircraft comes to a full stop, still level and intact. The flames on the side of the aircraft with the ruptured wing begin to melt the acrvlic polymer windows and begin to burn through the fuselage.
During the next minute, that is within about 60 to 120 seconds of the initial impact, a portion of the aircraft's interior is ablaze and the cabin begins to fill with a dense, black, acrid smoke. Seat cushions begin to catch fire and the smoke in the cabin stings the passengers' eyes shut. The smoke and poisonous gases incapacitate the weak and elderly almost immediately and the other passengers shortly thereafter. Passengers who are still conscious blindly attempt to crawl toward an exit which, quite typically, is not visible because of their shut eyes.
After about two minutes from the initial impac the cabin is an inferno. All passengers remaining in it are asphyxiated by smoke, poisoned by toxic gases and incapacitated, that is unconscious and unable to move. Thereafter, they are burnt to death by flames.
There are indications that a substantial number of passengers in low impact aircraft crashes could be saved. Studies have shown that between 1969 and 1983, over 60% of the fatalities in such crashes were not caused by impact, but by suffocation due to the inhalation of toxic fumes and smoke. For example, the majority of the 583 passengers who died at the Tenerife (Canary Islands) disaster of 1982 expired from smoke and toxic gas inhalation and not from burns. Further, studies have shown that over 80% of the passengers who died by fire are not burned to death instantly. Instead, they are first felled by inhalation of smoke and gases emitted by the burning cabin materials, and thus are unable to escape.
One of the major contributors to the almost insurmountable odds against survival faced by surviving passengers in burning aircraft are the dense, blinding smoke emitted by polyurethane seat cushions. These cushions ignite easily and emit such lethal gases as acrolein, phosgene, carbon monoxide, surphuric acid and hydrogen cyanide.
Many of these fatalities could be prevented if the passengers' heads, typically the only fully exposed part of their bodies, could be protected from the hostile environment and if the breathing air could be cleansed of toxic and choking ingredients by providing each passenger with a protective hood and a breathing mask which he could take with him during his escape attempt after he leaves his seat. For a variety of reasons, this has not happened in the past. In part, this is believed to be due to impractical designs. In part this is due to the high cost of the required cabin modifications to accommodate such masks. Lastly, this is also due to the inability of existing smoke hoods to provide the required head protection and air cleansing. The applicants are advised that studies have determined that it would be over 20 times more expensive for airlines to implement the use of existing smoke hood-breathing mask designs than to pay the average $500,000.00 death settlement to the survivors of persons who perish in aircraft crashes.